A Research On Reaction Time

Introduction

The purpose of this lab was to explore the relationship between visual reaction time, auditory reaction time, and movement time. The functional definition of a reaction time is the amount of time from the onset of a stimulus to the initiation of response, and movement time is defined as the time from which a movement is initiated to completion of the movement. Two relationships are being explored in this experiment. The first is investigating which will produce a faster reaction time, visual or auditory. The second poses the question, if a participant has a fast reaction time, will they in fact have a fast movement time as well? In other words, is there an interdependence at play?

The first hypothesis is that visual reaction time will have a faster reaction time that auditory reaction time. This hypothesis was arrived at through the prior knowledge that the speed of light is significantly faster than the speed of sound, especially in air, and the prediction that a light stimulus would reach the participant faster than an auditory stimulus could, resulting in a faster visual reaction time, or in other words, a reaction time closer to zero.

The second proposed hypothesis is that there is an interdependence at play between reaction time and movement time. It is reasonable to assert this given the prior knowledge that a quick reaction time typically accompanies a quick movement time, especially in the instance of sports or athletics. For example, a baseball player must be able to react fast in order to initiate a movement to hit a baseball, and also a quick movement time to bring the bat around full swing in order to hit the ball. There are numerous other examples, but it is a reasonable conclusion to draw that there is some dependence at play with reaction time and movement time. Additionally, in this first lab we will be practicing using excel and excel function, such as calculating correlations and standard deviations, among others, as well as making charts for reports.

Methods

Participants: For this lab, 23 students paired up in groups of two and conducted each experiment. Half would focus on visual reaction time, while the other half focused on auditory reaction time. Instructions were given by the professor at the beginning of the lab.

Procedure: The lab included the use of a reaction movement timer for auditory reaction time measurements, and the use of a computer program for visual reaction time measurements. Three trials of each station were completed by each student, so three trials of visual reaction time and three trials of auditory reaction time. Each trial, regardless of what was being measured, an external stimulus would be generated (in this experiment, in the form of a light on the computer screen or a ‘beep’ from the reaction movement timer) and a response to be completed as quickly as possible. Data from each trial was recorded by a partner, and then averages of each trial were calculated, and subsequently entered into a group excel document.

Results

In figure two below, the averages of each time are recorded. It is clear to see that auditory reaction time had a lower, or decreased, reaction time than visual reaction time did. The average reaction time for the visual stimulus was 275.35 ms, auditory was 212.43 ms, and average movement time was 393.65 ms. The medians for these respective times were 263, 215, and 443.

The standard deviations for the three average times, respectively again, were as follows; 29.04, 25.19, and 62.93. The standard deviations for reaction times here are reasonable considering the scale of data, though the standard deviation for movement time was significantly larger considering the scale, and indicates much more disparity in the data recorded than that of the reaction times. Refer to Figure one below for a synopsis of this data. The independent variable in this experiment is the stimulus, and the dependent variable is the reaction time/movement time.

VRT ART MT

Mean 275.35 212.43 393.65

Median 263 215 443

Standard Deviation 29.04 25.19 62.93

Figure 1*

*Figure 2

Additionally, the relationship between auditory reaction time and movement time is visualized below in figure 3. The correlation for this relationship is .157, which is defined as the two variables being independent of each other, which is clearly illustrated in the scatter plot in figure 3. There is no detectable relationship between reaction time and movement time, and a correlation of .157 proves this.

Figure 3*

Discussion

The data from this experiment refutes the original hypothesis that visual reaction time is faster than auditory reaction time, and instead proves that the opposite is true. There was an over 60 ms difference between auditory and visual reaction time, which proves with some significance that auditory is definitively faster. Additionally, it refutes the second hypothesis that there is an interdependence at play between reaction time and movement time. The small correlation coefficient (.157) proves this, and the lack of dependence is further illustrated in the scatter plot.

The answer to the question of why these things are true lies in the anatomy of the brain. The visual cortex is located in the occipital lobe of the brain, while the auditory cortex lies in the temporal lobe of the brain. Because it takes auditory stimuli less time to reach the auditory cortex than it takes visual stimuli to reach the visual cortex, the reaction time of auditory stimuli is faster1. The lack of correlation between auditory reaction time and movement time can be attributed to each individual and their ability to make fast and accurate movements while also in the presence of uncertainty, both applications of Fitts’ and Hick’s Laws2.

Overall, understanding reaction time and movement time is critical to our everyday lives, and knowing that auditory reaction time is faster than visual reaction time is equally important too. For example, if one knows that his/her auditory reaction time is much faster than their visual reaction time, they might keep the radios in their cars at a lower volume, or try to keep out more distractions, because the split second head start they might have on initiating a response/movement time in the event of a dangerous road hazard or accident, could just be enough to save their lives. Having this knowledge in day to day activities might encourage us to minimize auditory distractions when important tasks are at hand.